A New Look At Acid Rain

March 29, 1986|By William W. Marion, executive vice president of the Council for Agricultural Science and Technology.

President Reagan`s special task force headed by former Transportation Secretary Drew Lewis is said in a recent Tribune editorial to have found that natural sources of sulfur dioxide and nitrogen oxides are relatively insignificant contributors to acid rain. It noted that the total emissions of the Mt. St. Helens volcano in its most active year were about the same as the annual sulfur emissions of two large coal-fired power plants.

It is only fair to point out, however, that selection of sulfur dioxide emissions from Mt. St. Helens makes a good basis for the argument that natural sources of sulfur dioxide are relatively insignificant contributors to acid rain because Mt. St. Helens is recognized as a low-sulfur volcano.

The principal concerns about acid rain have been its presumed effects on plants, principally forests, and the fish in lakes. We know that if we apply enough sulfuric acid, nitric acid or both to plants, they will die. Consequently, when we observe forest declines in areas where the precipitation is relatively acid, intuition suggests that these acids cause the damage to the trees. But that does not constitute scientific proof that the acid rain caused the damage.

Scientific experiments have been done with simulated acid rain in an attempt to reproduce the damage to vegetation attributed to acid rain. These experiments have failed to verify that acid rain is the culprit. Greater acidity is required to injure the foliage. As a consequence of these experimental findings, the scientific community is coming to the conclusion that acid rain is not the cause of the forest decline.

Meanwhile, evidence has been accumulating that the gas ozone is perhaps the primary malefactor. Ozone is a highly reactive form of oxygen that may be formed by interaction between gaseous organic compounds and certain gaseous nitrogen oxides produced in automobile engines and other high-temperature installations where air is present.

Current indications are, therefore, that acid rain is not the cause of forest decline. It is merely associated with the decline.

The current scientific evidence indicates that we are riding the wrong horse. The problem is the nitrogen oxides. The methods that have been used to catch the sulfur dioxide in smoke stacks are essentially ineffective in trapping the nitrogen oxides.

A new process developed in Japan, called the Ebara process, is able to remove from flue gas much of the nitrogen present in oxide forms. Being tested now in this country, the Ebara process forms a solid product containing ammonium nitrate and ammonium sulfate, which can be used as a fertilizer.

The mixture of ammonium nitrate and ammonium sulfate that is produced by the Ebara process is an acid-forming fertilizer. In effect, the Ebara process would reduce the acidity of the rainfall and would reduce the distribution of free fertilizer on farmland. There seems to be no free lunch, even in the acid rain business.

The interaction of acid rain with surface waters is another interesting subject. In the Northeast, we have a number of lakes that are relatively acid, and these are commonly pointed to as ``Exhibit A`` in the acid rain controversy. It is not yet clear how much of the acidity results from acid rain, how much results from natural processes in the lakes and how much results from the waters draining into the lakes from the surrounding land.

Some scientists have estimated that neutralizing with lime the acid in 180 ``dead`` lakes and ponds in the Adirondack region would cost $1 million. That may seem like an exorbitant price to pay for the privilege of sport fishing in those waters. On the other hand, it is considerably more economical than Mr. Lewis` proposed $5 billion program.